The assembly of amyloidogenic yeast sup35 as assessed by scanning (atomic) force microscopy: an analogy to linear colloidal aggregation?

Amyloidosis is a class of diseases caused by protein aggregation and deposition in various tissues and organs. In this paper, a yeast amyloid-forming protein Sup35 was used as a model for understanding amyloid fiber formation. The dynamics of amyloid formation by Sup35 were studied with scanning force microscopy. We found that: 1) the assembly of Sup35 fibers begins with individual NM peptides that aggregate to form large beads or nucleation units which, in turn, form dimers, trimers, tetramers and longer linear assemblies appearing as a string of beads; 2) the morphology of the linear assemblies differ; and 3) fiber assembly suggests an analogy to the aggregation of colloidal particles. A dipole assembly model is proposed based on this analogy that will allow further experimental testing.